Officials testing seal at BP's busted Gulf well

NEW ORLEANS (AP) - In the strongest indication yet that BP's broken oil well in the Gulf of Mexico may be plugged for good, officials on Thursday said they're conducting tests to determine if further work to seal the well is needed.

A final decision was expected Friday on whether crews need to go ahead with drilling relief wells to allow for a so-called "bottom kill," in which mud and cement are pumped from deep underground to permanently seal the well.

Retired Coast Guard Adm. Thad Allen, the Obama administration's point man on the oil spill, said at a news conference that an earlier effort to temporarily plug the well may have had the unintended effect of creating a permanent seal.

However, he cautioned it's more likely that drilling will continue on two relief wells, which have long been said to be the only way to ensure the blown-out well doesn't leak again. That work has been delayed because of bad weather and wouldn't resume for about another four days, if testing shows it's needed.

Last month, after a cap meant to be temporary was fitted on top of the broken well and halted the oil flow, crews pumped in mud and cement from above in a so-called "static kill." Some of the cement may have gone down into the reservoir, come back up and plugged the space between the inner piping and the outer casing - which is what engineers were hoping to do with the bottom kill, Allen said.

"A bottom kill finishes this well. The question is whether it's already been done with the static kill," he said.

Officials are testing pressure levels in that space between the inner piping and outer casing. Rising pressure means the bottom kill still needs to be done, Allen said. Steady pressure may mean cement already has plugged that space.

However, Allen said tests won't show how much cement is in the space, making the original plan for a bottom kill a better way to ensure the well is permanently plugged.

"What we hope we'll find is an immediate rise in pressure," he said. "It would be more problematic and quizzical if there were no immediate change in pressure."

A decision not to proceed with the relief well would bring an unexpected conclusion to the phase of the disaster that began on April 20 with an explosion on the Deepwater Horizon drilling rig. The federal government estimates that 206 million gallons of oil spilled into the Gulf, the worst offshore spill in U.S. history.

Although the flow into the waters of the Gulf was stopped nearly a month ago with a temporary cap, officials have maintained that they wouldn't declare victory until the well is sealed for good.

Because of that, stopping without the expected bottom kill might not win immediate acclaim from the public, said Eric Smith, associate director of the Tulane Energy Institute.

"It doesn't make much sense to drill a hole into cement to pump more cement into it," he said. "But it's a public relations nightmare to explain that."